CACHE Process Design Case Studies

• Volume 1: Separation System for Recovery of Ethylene and Light Products from a Naptha Pyrolysis Gas Steam
• Volume 2: Design of an Ammonia Synthesis Plant
• Volume 3: Design of an Ethanol Dehydrogenation Plant
• Volume 4: Alternative Fermentation Processes for Ethanol Production and Economic Analysis
• Volume 5: Retrofit of a Heat Exchanger Network and Design of a Multiproduct Batch Plant
• Volume 6: Chemical Engineering Optimization Models with GAMS
• Volume 7: Design of an Ethylbenzene Production Plant
• Volume 8: Nitrogen from Air (on-line version available at no cost)
• Volume 9: Conceptual Design of Second Generation Bioethanol Production via Gasification of Lignocellulosic Biomass
• Volume 10: Conceptual Design of the Supply Chain and Production Facility of Lignocellulosic Bioethanol via Hydrolysis
• Volume 11: Conceptual Design of an Aromatics Plant from Shale Gas

CACHE Process Design Case Study Vol. 4

"Alternative Fermentation Processes for Ethanol Production"

The objective of this case study is the preliminary design and economic evaluation of a fermentation process for the production of ethanol from a molasses feedstock. The intent is to expose the student to some non-traditional chemical engineering processes and to the expanding field of biotechnology. The scope of the study is such that groups of 2-3 students should be able to complete the design in about 30 days. The major focus of this design is the creation and rational development of a suitable process flowsheet, simulation of the flowsheet by the simulator FLOWTRAN, and economic evaluation and cost minimization of the final process.

The problem begins with the specification of the plant operating requirements. The type of fermentor to be used as well as plant operating conditions are left open. Suggested fermentors include batch, CSTR, CSTR w/cell recycle as well as a novel extractive fermentor based on the use of hollow fiber membranes (HFEF). The choice of the fermentor will affect the nature of the flowsheet and lead to several design alternatives which the students will have to screen before arriving at a workable flowsheet that is ready for simulation. This case study includes a floppy disk with input files for the simulator FLOWTRAN as well as a program written in BASIC to evaluate the performance of CSTR fermentors.

The problem statement was posed by Professors Steven LeBlanc and Ronald L. Fournier and prepared under their supervision by the student Samer Naser at the University of Toledo.

CACHE Process Design Case Study Vol. 5

"Retrofit of a Heat Exchanger Network and Design of a Multiproduct Batch Plant"

This volume contains two short design projects that can be developed by groups of 2-3 students in about two weeks. As opposed to the large projects that are commonly used in a design course, the objective of the case study is to expose students to a greater variety of problems and which are of current industrial significance.

The first problem deals with the retrofit of a heat exchanger network consisting of 8 exchangers with 5 hot and 3 cold processing streams as well as steam and cooling water. The layout of the network and areas of the exchangers are also given. The objective is to determine a retrofit design that can reduce the energy consumption within specified limits for the capital investment and payout times. This problem requires examination of alternatives for the level of energy recovery, matching of streams, addition o f area, and removal or reassignment of existing exchangers and piping. This problem can be used to illustrate basic concepts of heat integration, as well as the application of computer software such as Target II, THEN, MAGNETS and RESHEX. The second desig n problem deals with the design of a batch processing plant that has to manufacture 4 different products, all of which require 5 similar processing steps (reaction, product recovery, purification, crystallization and centrifuge). An important aspect of th is problem is that the production schedule and inventory must be anticipated at the design stage. Furthermore, this problem also requires analyzing alternatives for merging processing tasks into single units, and using parallel units with and without intermediate storage. The use of Gantt charts is emphasized to examine some of these alternatives. The case study also includes two sets of homework problems with solutions that can be used to provide the basic background for the two problems.

This case study has been prepared by the students Richard Koehler and Brenda Raich at Carnegie Mellon University under the supervision of Professor Grossmann who developed the problem statements and educational material.

CACHE Process Design Case Study Vol. 6

"Chemical Engineering Optimization Models with GAMS"

The objective of this case study is to provide a set of chemical engineering problems to supplement optimization courses at both the undergraduate and graduate level. This case study should also be useful in other courses and to practicing engineers to learn about GAMS and its applications.

GAMS is an algebraic modelling system in which the user need not be concerned with details of providing the interfaces with various optimization codes. Instead, the GAMS environment allows the user to concentrate on the modelling of problems, which u ltimately is the main skill that is required for the successful application of optimization in practice. This case study covers applications at various levels of complexity in the following areas: (a) Planning and scheduling of batch and continuous proce sses, (b) Chemical and phase equilibrium, (c) Design of heat exchanger networks, distillation columns and batch processes, (d) Synthesis of reaction paths, heat exchanger networks and distillation sequences, (e) Optimization of dynamic and distributed par ameter models. These problems are modelled as linear, nonlinear and mixed-integer optimization problems.

This case study describes in detail the formulation and solution of a total of 22 optimization problems that cover the different areas cited above. Exercises are also given for each problem. In addition, the case study includes:

1. Special student version of GAMS for IBM-PC and compatibles in 3 1/2 in diskettes. The MINOS, ZOOM and DICOPT++ codes are inclu ded in this GAMS version which can handle problems with up to 1000 nonzero elements in the Jacobian matrix.
2. GAMS input files for all the problems; these are extensively documented.
3. GAMS User's Guide.

This case study has been prepared by faculty and students from Carnegie Mellon University, Northwestern University and Princeton University under the coordination of Ignacio E. Grossmann. GAMS Development Corporation, the Licensing Technology Office at Stanford University, XMP Optimization Software and Sunset Systems have donated the computer software for this case study.

CACHE Process Design Case Study Vol. 7

"Design of an Ethylbenzene Production Plant- Preliminary Design and Economic Analysis"

The objective of this case study is the preliminary design and economic evaluation of an alkylation process for the production of ethylbenzene from ethylene and benzene. The intent is to expose the student to a traditional chemical engineering process. The scope of the study is such that groups of 3-4 students should be able to complete the design in 3 months. The major focus of this design is the creation and development of a suitable process flowsheet, simulation of the flowsheet by the simulator HYSYS, economic evaluation and cost minimization, and HAZOP analysis of the final process.

The problem begins with a statement of the design specifications. Students are then required to consider alternatives for the reactor type (fixed or fluidized bed), reactor conditions (liquid or vapor phase) and separation scheme. These choices affect the layout of the flowsheet and lead to several design alternatives. Students are expected to analyze the various process alternatives based on economic, safety, and environmental factors. Included in this case study is a floppy disk containing the HYSYS simulation file and GAMS input files for modeling the heat integration.

The problem statement was posed by Professor Costas D. Maranas and prepared by James E. Lease, Gregory L. Moore, Ryan M. Scofield and Joseph D. Sevick in the department of Chemical Engineering at the Pennsylvania State University. Mike Kalp was also involved in putting the case study together, and he was supported by the ECSEL program at Pennsylvania State University.

This case study is available in two forms:

1. Hardcopy with binder and disk with HYSIS input file

          CACHE Supporting department $50

          Non-supporting department $90

    b. CD-ROM containing text of case study and HYSIS file. Large flowsheet diagram is also provided.

        CACHE Supporting department $30

        Non-supporting department $50

CACHE Process Design Case Study Vol. 8

"Nitrogen from Air" (on-line version available at no cost)

Nitrogen from Air

My design Group has just finished the development of a web-based case study and tutorial entitled: Nitrogen from Air. This represents a significant advance over the one developed previously. It includes detailed process descriptions, downloadable reports and simulation input files, and calculators and animations.

Larry T. Biegler, Carnegie Mellon University

CACHE Process Design Case Study Vol. 9

"Conceptual Design of Second Generation Bioethanol Production via Gasification of Lignocellulosic Biomass"

This case study deals with the conceptual design of production processes for obtaining ethanol using switchgrass as raw material using the thermal route. The switchgrass is gasified with either low pressure indirect gasification or high pressure direct gasification to produce syngas. The resulting gas is reformed and cleaned up in a series of stages to remove solids and sour gases. In the next step, the syngas is used to obtain ethanol either via fermentation or by catalytic synthesis. Finally, the products are purified using different technologies for dehydration or ethanol recovery from a mix of alcohol. Two reports are presented from two groups of students. Based on the same initial information, the groups selected different flowsheets for the production of ethanol, the major difference being the choice of fermentation versus catalytic synthesis. The reports consist of three memos: literature survey and selection of initial flowsheet, mass and heat balances of selected flowsheet, and economic evaluation. Short-cut models are used and the reasons behind the selection among the alternatives and the results are discussed. Background material and teaching aids are also included.

CACHE Process Design Case Study Vol. 10

"Conceptual Design of the Supply Chain and Production Facility of Lignocellulosic Bioethanol via Hydrolysis"

This case study deals with the conceptual design for the production of lignocellulosic ethanol via hydrolysis including plant location, selection of the field for growing the biomass, transportation and storage to supply 80MMgal/yr of bioethanol to Chicago and Pittsburgh. The switchgrass is to be pretreated to expose the polymers for hydrolysis obtaining the sugars. Next, the sugars are fermented to ethanol, and lignin is to be recovered. Finally, the products are purified using different technologies for dehydration of ethanol. Complete reports from two groups are presented. Each report consists of three memos: literature survey and selection of the plant location and initial flowsheet, mass and heat balances of selected flowsheet, and equipment sizing and economic evaluation. Reasons behind the selection among the design alternatives are discussed as well as the results that were obtained with short-cut models. Background material and teaching aids are also included.

CACHE Process Design Case Study Vol. 11

"Conceptual Design of an Aromatics Plant from Shale Gas"

In this case study shale gas and condensates from the wet gas (e.g. ethane) are used as raw material instead of more expensive crude oil to produce aromatics (benzene, toluene, xylene). One of the interesting points in the case study is the number of different flowsheets that can be synthesized. Students must first screen different alternative chemical pathways based on methane and ethane to decide on the specific process. Furthermore, apart from the use of Mathcad or Excel for preliminary process calculations, process simulation using ASPEN-PLUS is used for the development of the detailed mass and energy balances of the plant, while ASPEN-ENERGY ANALYZER is used for energy integration and synthesis of heat exchanger networks. The case study contains detailed flowsheet designs from two design groups at Carnegie Mellon. The designs are documented through 3 memos that cover literature survey and preliminary screening, mass and energy balances and economic evaluation. Background and supporting material for the instructor is also included.

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